Control system



Jan. 22, 1929. 1,699,762

B. H. SMITH CONTROL SYSTEM Filed Feb. 5, 1925 WITNESSES: w 1 INVENTOR Q Begum/n h. 5/71/7h.

Patented Jan. 22, 1929.

UNITED STATES PATENT OFFICE.

BENJAMIN B; SMITH, OF SWISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELEQTBIO & MANUFACTURING COMPANY, A. CORPORATION OF PENNSYLVANIA.

CONTROL SYSTEM.

Application fll'ed February 8, 1925-. Serial No. 6,536.

M invention relates to control systems and particularly to load control systems for systems of distribution. 7

One object of my invention is to provide a control system that shall have means for controlling auxiliar or stand-b generators to assume the peak oads where t e average load on a system is suppliedby a main source of supply.

Another object of my invention is to provide a control system for an auxiliary generator that functions in accordance with the varying load; such as a railway load upon another source of supply which may e a relatively great distance away from the auxiliary machine.

Patent No. 1,199,571, to J. E. King, dated September 28, 1916, discloses a load-regulating system comprising a main generator and .20 an auxiliary generator, the latter being controlled in such manner that it will assume all of the load on the system in excess of a certain value.

The present invention is an improvement upon the system disclosed in said patent and comprises a wattmeter connected in the main supply circuit that is adapted to control the auxiliar generator, the controlling means being unadected by the distance separatin the main and auxiliary generators in case t ese machines are widely se arated.

For a clear understan 'ng of my invention, reference should be had to the accompanying drawings, wherein Fig. 1 1s a diagrammatic view of an alternating-current system embodying my invention, and

Fig. 2 is a similar view of a modification thereof.

Referring to Fig. 1, an alternating-current distribution system is shown comprising a main supply circuit 1, an auxiliary supply circuit 2 and a plurality of distribution circuits 3 connected to both of said supply circuits. A three-phase alternator 4 is connected to the main sup 1y circuit and supplies power to the distri ution circuits under normal conditions. A second three-phase alternator 5 is connected to the auxiliary supply circuit to supply the power to the system in excess of a redetermlned value.

One applicatlon of my invention is in railway distribution systems in which the railway company purchases power from a sepa- -railway distribution systems are usually extensive, the auxiliary source 5 may be connected to the system at. a point that is a relatively great distance away from the point of connection of the main source. Accordingly, if a control circuit is used for controlling the auxiliary source of power in accordance with the load on the main source, it is desirable to provide a transmission system that is not affected by the variations in resistance or the other characteristics of the control circuit.

The control system shown comprises an integrating wattmeter 6 connected to the main supply circuit 1 to measure the power supplied by the generator 4to the distribution circuits 3. A control circuit 7 extends from the wattmeter 6 to a controlling device 8 associated with the auxiliary generator 5. The auxiliary generator 5 is driven by a prime mover 9, such as a water wheel or steam turbine. A governor 10 controls the speed of the prime mover 9, and a valve 11 controlled by a pilot motor 12 controls the supply of water or steam to the prime mover 9.

The wattmeter 6 is adapted to generate current impulses at a rate proportional to the power measured by the wattmeter, and a Kelvin balance 13 responsive to said current impulses controls the pilot motor 12 to regulate the load on the auxiliary generator 5.

The wattmeter 6 is of the usual motor .or induction ty e and the rotating element thereof is provided with a commutator 14 controlling the circuit of an impulse relay 15. As the motor element of the wattmeter. rotates, the circuit of the impulse relay 15 is alternately closed and broken at a rate that is proportional to the power traversing the main sup ply circuit 1. The impulse relay 15 controls an impulse relay 16 associated with the auxiliary generator over the control circuit 7 The '17 are constant, the average current traversing the Kelvin balance 13 is proportional to the rate of operation of the impulse relay 16 and,

. consequently, to the energy tranversing the main supply circuit 1.

The movable element 'of the Kelvin balance,

13 has a relatively large inertia and is highly damped so that the average torque is depend ent upon the fre uency of the current imulses even when t ey are impressed upon the alance at a slow rate, such as only one impulse in two or three seconds.

Under normal conditions, the generator 4 supplies the power demand and the generator 5 is running idle. If the load demand increases above a certain value, the frequency of the current impulses generated by the wattmeter 6 actuates the Kelvin balance 13 and controls the pilot motor 12 in such manner as to open the valve 11 and cause the generator 5 to assume the increment of load.' When the load decreases again, the frequency of the current impulses 1n the control circuit 7 is lessened and the Kelvin balance 13 actuates the pilot motor 12 to close the valve 11 and transfer the total load to the main generator 4. Since the operation of the Kelvln balance 13 is dependent solely upon the frequency of the current impulses in the control circuit 7, the accuracy of the controlling operation is not affected by variations in the resistance of 1 i the control circuit and, therefore, the control may be exercised over relatively great distances.

In Fig. 2, I have shown a modification of my invention comprising a direct-current distribution system. A 1 0t motor 12 is controlled in'accordance w1th the load .on the main generator through the instrumentality of the Kelvin balance 13 in the same manner as shownin Fig. 1. A direct-current auxiliary generator 19 connected to the distribution system is controlled by a field rheostat 20 actuated by the pilot motor 12. In case the load increases above a predetermined value, the pilot motor 12 is actuated insuch a direction as to decrease the resistance 20 thereby increasing the field excitation and causing the enerator 19 to assume the increment of loaf.

I do not consider that my invention is limited to the precise embodiment shown and described, as it embraces the general conception of the remote control of a dynamo-electric machine in accordance with the load in a supply circuit. Accordingly, I do not wish my invention limited in scope except as indicated in the appended claims.

I claim as my invention:

1. A system comprising a main generator,

an auxiliary generator, a wattmeter associated with the main generator, a currentimpulse sending device operated by the wattmeter, load-regulating means for the auxiliary generator and means including said wattmeter and current-impulse device for controlling said load-regulating means.

2. A system comprising a supply circuit, a wattmeter connected therein, a current-impulse sending device operated by the wattmeter, a generator for supplying energy to the supply circuit,,load regulating means for the generator andmearisincludingsaidwattmeter and current-impulsedevice for controlling said load-regulatlng means in accordance with the load on said supply circuit.

3. A system comprising a sup ly circuit, a wattmeter connected therein, a ynamo-electric machine at a remote point from said wattmeter for supplying energy to the supply'circuit, conductors extending from said wattmeter to said dynamo-electric machine, means for transmitting the indications of said wattmeter over said conductors, said means bein unaffected by the resistance of said con uctors, and means connected to said conductors for controlling said machine in accordance with the power traversing said supply circuit.

4. A system comprising a main generator, an auxiliary generator at a relatively great distance therefrom, a control circuit between said generators, means for transmitting an indication of the load on said main generator over said circuit, said means being so arranged that the accuracy of transmission is unaffected by variations in the resistance of said circuit, and means responsive thereto for causing the auxiliary generator to assume all load in excess of a certain value.

5. A system comprising a supply circuit, a second supply circult, a wattmeter in the firstmentioned circuit, a generator connected to said second supply circuit, means for modifying a periodic controlling current at a rate that depends upon the power measured by said wattmeter and means for controlling said generator in accordance with the periodicity of said controlling current.

6. A system comprising a supply circuit, a wattmeter connected thereto, means for enerating current impulses at a rate depen ing upon the power measured by said wattmeter, a dynamo-electric machine for supplying energy to the supply circuit and means responslve to said current impulses for controlling said machine.

7 A system comprising a supply circuit, a second supply circuit, a wattmeter in the first-mentioned circuit, a generator connected to the second supply circuit, a control circuit connecting the wattmeter and the generator, means for producing a current in said control circuit in accordance with the power measured by said wattmeter, and means connected to said control circuit for causing the gen erator to assume the increments of load on the system.

8. A system comprising a supply circuit, a wattmeter connected thereto, means for enerating current impulses at a rate depen ingupon the power measured by said wattmeter,

energy to the supply circuit and means re sponsive to said current impulses for render- 1 In testimony whereof, I have hereunto subscribed my name this 23rd day of January 16 1925. a dynamo-electric machine for supplying;

BENJAMIN H. SMITH. 

